I. Field of the Invention
The present invention relates generally to display devices implementing Field Emission Display (FED) technology. More specifically, the invention relates to a method for increasing the emission current of the current emitters of a Field Emission Display (FED).
II. Description of the Related Art
Until recently, the cathode ray tube (“CRT”) had been the primary device for displaying information. While having sufficient display characteristics with respect to color, brightness, contrast, and resolution, CRT's are relatively bulky and consume large amounts of power. In view of the advent of portable laptop computers, the demand has intensified for a display technology which is light-weight, compact, and power efficient.
One available technology is flat panel displays, and more particularly, Liquid Crystal Display (“LCD”) devices. LCDs are currently used for laptop computers. However, these LCD devices provide poor contrast in comparison to CRT technology. Further, LCDs offer only a limited angular display range. Moreover, color LCD devices consume power at rates incompatible with extended battery operation. Lastly, a color LCD type screen tends to be far more costly than an equivalent CRT.
FED technology has recently come into favor as one technology for developing low power, flat panel displays. This technology uses an array of cold cathode emitters and cathodoluminescent phosphors for conversion of energy from an electron beam into visible light. Part of the desire to use FED technology for flat panel displays is that such technology is conducive to producing flat screen displays having high performance, low power and light weight.
In FED structures and devices a plurality (array) of microelectronic emission elements are employed to emit a flux of electrons from the surface of the emission element(s). The emitter surface, referred to as a “tip”, is specifically shaped to facilitate effective emission of electrons, and may for example be conical, pyramidal, or ridge-shaped in surface profile, or alternatively the tip may comprise a flat emitter surface of low work function material.
In the construction of FED current emitters, various materials are deposited onto a substrate to form the device. Thereafter, a panel containing spaced phosphors is sealed to a panel containing the emitters under conditions where the temperature is approximately 400 degrees Celsius. When the material used to construct the FED current emitter tip, an amorphous silicon doped with boron or phosphorus, is deposited, native oxides form on the tip due to exposure to the atmosphere. This change in the chemical nature of the tip results in an increased work function yielding a decrease in the current emission of the tip nearly ten fold. As a general principal the work function is an instrumental factor in the resulting current emission. The practical effect is the manifestation of a display which is dimmer than that desired or expected, often resulting in an increase in power usage in order to try to achieve a brighter display.